A 24-hour strike has brought chaos to the French transport system today as trade unions mobilised a mass protest against planned state pension reforms.

On what has being dubbed "Black Tuesday" by the French media, planes, trains and buses across the country ground to a halt, schools were shut and hospitals and post offices were affected as public sector workers stayed at home. It is being seen as the biggest challenge yet to the centre-right government of prime minister Jean-Pierre Raffarin.

France's DGAC aviation authority said it expected 80% of international and domestic flights to be grounded. France's national airline, Air France, said it would run all its long-haul flights, but has been forced to cancel two-thirds of national and medium-distance services.

British Airways, which operates flights to France from seven UK airports, was operating only 10 of its normal 120 daily French flights. The airline said passengers affected would be offered the choice of a rebooking or a refund. BMI and its budget airline, bmibaby, were also having to cancel flights.

Budget airline easyJet had to cancel around 60 of its 80 French flights, while rival carrier Ryanair cancelled more than 20 flights, with five others delayed and only three operating to schedule.

Morning cross-Channel traffic between Calais and Dover was also halted. The port of Calais was due to be closed for part of the day and P&O Ferries said it was not expecting to operate Dover to Calais services from early morning to mid-afternoon. The company added that it was not accepting any day-trip passengers tomorrow and that tickets for today would be honoured on alternative dates.

However, the Channel Tunnel Eurotunnel shuttle trains as well as the London to Paris and Brussels high-speed Eurostar trains were expected to run normally.

Two-thirds of French mainline services were cancelled by the state railway company, SNCF, even though its workers will not be directly affected by the government's plans.

Parisians were forced to walk, cycle or skate to work this morning, as the metro system had all but closed down. The Paris transport authority said that most metro lines were completely closed.

There was some good news for commuters, however, as a walkout by workers at motorway tollbooths ensured a free ride for some motorists.